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CVE-2018-15126: Libvnc Project Libvncserver: Use after free

CVE-2018-15126 is rated critical with a CVSS v3.0 base score of 9.8 and NVD lists 3 affected products, including Libvnc Project Libvncserver. Per its scoring, it can be exploited over the network, without authentication, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available.

Vulnerability description

LibVNC before commit 73cb96fec028a576a5a24417b57723b55854ad7b contains heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution

Severity breakdown

CVSS v3.0 9.8: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
Attack complexity: Low. No special conditions; the attack can be repeated reliably.
Privileges required: None. No account or prior access is needed.
User interaction: None. No action from any user is needed.
Scope: Unchanged. Impact stays within the vulnerable component.
Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-416: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

Affected products

Libvnc Project Libvncserver: before 0.9.12
Canonical Ubuntu Linux: 14.04; 16.04; 18.04; 18.10
Debian Linux: 8.0; 9.0